The invention relates to apparatus for the remote measurement of physical parameters in which the advantages of optical fibre cables and optical fibre sensors are exploited for use within the oil industry. The invention has important applications for monitoring oil and gas reservoirs, for stack monitoring and monitoring within refineries.
As oil and gas reserves have been consumed over the years, the extraction of the oil and gas has become increasingly more difficult under more demanding conditions. Accordingly, there is a need for the reserves to be monitored to a higher quality than hitherto. The potential payback is reducing operating costs and increasing the yield from individual reservoirs. The invention also impacts on operational and environmental safety.
There is a growing recognition that continuous dynamic sampling of downhole conditions within oil wells can generate dynamic data streams that can be processed and turned into valuable new information. Modern computer aided visualisation techniques make it much easier for production and reservoir management teams to detect and interpret changes in wellbore conditions, near-wellbore conditions and even changes in the reservoir further away from the immediate wellbore. This information can be fed back into computer models of the reservoir that are used to simulate the oil production system. These reservoir models include geologic data, seismic data, and assumptions based on past logging and exploration activity and shut-in tests on wells. By expanding the number of parameters that are sampled and by increasing the frequency of sampling, the model can be improved to reveal finer details of the reservoir properties. The benefits of this improved information are that asset managers are better positioned to anticipate degradation in the well structure, to anticipate water and gas coning and to identify regions of the reservoir where oil is left behind.
GB-A-2284257 relates to apparatus for the remote measurement of physical parameters. Experience over many installations has shown that the technique is not always reliable especially when deploying optical fibre sensors through steel hydraulic control lines in oil wells where the steel hydraulic control lines contain many bends and curves. The problem is that optical fibre cables can become stalled in the control line which can lead to tangling and possible destruction of the optical fibre cable in the hydraulic control line.
An aim of the present invention is to improve on known apparatus by improving the reliability of the apparatus needed to install and retrieve an optical fibre sensor for the measurement of physical parameters.
According to a non-limiting embodiment of the present invention, there is provided apparatus for the remote measurement of physical parameters, which apparatus comprises a sensor for sensing one or more physical parameters, sensor instrumentation for interrogating the sensor and making a measurement, a cable for extending between the sensor and the sensor instrumentation, a conduit for extending to a measurement location and which is of such a cross-sectional size that it is able to accept the cable and the sensor, and cable installation means for installing the sensor and the cable through the conduit and for placing the sensor at the measurement location, the cable installation means being such that it includes means for propelling a fluid along the conduit, and the conduit being such that it preferably contains a lead-section for providing sufficient fluid drag on the cable as it enters the conduit from the cable installation means to ensure that the sensor is able to be transported through the conduit. The means for propelling the fluid along the conduit can include any such known apparatus, as for example a pump, a venturi, gravity, and a compressor.
The sensor can be one or more optical fibre sensors. These optical fibre sensors can be sensors for measuring temperature, distributed temperature, pressure, acoustic energy, electric current, magnetic field, electric field, or a combination thereof.
The sensor can be a flow sensor based on combining the outputs from more than one sensor and applying an algorithm to estimate flow.
The sensor can be an array of optical fibre sensors configured on the same optical fibre. The array of optical fibre sensors can include a plurality of optical fibre Bragg gratings each returning a signal whose wavelength varies with applied temperature, pressure or strain. The array of optical fibre sensors can be interrogated by time division multiplexing, wavelength division multiplexing or a combination of time division multiplexing and wavelength division multiplexing.
The array of optical fibre sensors can include a plurality of optical fibre interferometers constructed from pairs of optical fibre Bragg gratings where each optical fibre Bragg grating within any pair of optical fibre Bragg gratings reflects light at substantially the same wavelength. The array of optical fibre sensors can be interrogated using time division multiplexing, wavelength division multiplexing, coherent division multiplexing or a combination of all three multiplexing techniques.
The sensor can be a distributed sensor, wherein the distributed sensor provides more than one measurement along its length. The distributed sensor can be a distributed temperature sensor, a distributed pressure sensor or a distributed strain sensor. The distributed sensor can be a distributed optical fibre sensor based on the measurement of a combination of Raleigh scattering, Raman scattering or Brillouin scattering.
Examples of sensor instrumentation include the DTS 80 (the distributed sensor readout system manufactured by York Sensors), instrumentation for measuring the strain on an optical fibre Bragg grating, an optical interferometer measurement system for measuring acoustic energy, a polarimetric sensor measurement system, or a Brillouin scattering measurement read out system, or any other appropriate sensor instrumentation system as is described in many of the conferences on optical fibre sensor systems worldwide.
The cable can be one or more optical fibre cables, and is preferably a carbon coated optical fiber.
The means for propelling a fluid can be a hydraulic pump.
The means for propelling a fluid can be a gas bottle or a compressor.
The conduit can be high-pressure tubing with an inside diameter and pressure rating to make it suitable for deploying sensors to remote locations.
The conduit can be steel hydraulic control line commonly used in the oil and gas industry having an external diameter of xe2x85x9xe2x80x3 to xc2xexe2x80x3 (3 mm to 19 mm). Alternatively, the conduit can be coiled tubing commonly used in the oil and gas industry having an external diameter of xc2xexe2x80x3 to 2xe2x80x3 (19 mm to 50 mm) or greater.
The conduit can have a cross-sectional size that it is able to accept one or more cables and one or more sensors.
A pressure communication port can be connected to the conduit in order to communicate pressure from outside the conduit to a pressure sensor within the conduit. The pressure communication port can be an orifice or a valve.
A plurality of pressure communication ports can be connected to the conduit in order to communicate pressure from outside the conduit to either a single pressure sensor, a plurality of pressure sensors or to a distributed pressure sensor within the conduit. It can be desirable that flow of fluids within the conduit is prevented during pressure measurements. This can be achieved by sealing sections of the conduit or by controlling the plurality of pressure communication ports such that only one of the plurality of pressure communication ports is open at any one time.
The conduit can be a compound structure that includes an external wall of a rigid nature but with perforations that allow fluid pressure communication and an inner lining that is flexible and capable of accurately transmitting the external fluid pressure to the fluid inside the conduit. The external wall of this compound conduit has to be able to withstand operational pressures. The internal lining must be able to resist extrusion through the perforation under the operational pressures. The perforations are preferably carefully designed to minimise the risk of extrusion.
When a lead-in section is used, it should be long enough and straight enough so that fluid flow is sufficient to cause the cable and sensor to be propelled into and continue to be propelled into the conduit while the fluid is flowing, without causing the cable to stall in the lead-in section.
The lead-in section preferably does not contain substantial bends having bend radii less than 100 times the internal cross-sectional radius of the lead-in section.
The lead-in section preferably does not contain bends which cause the cable, when tensioned in the conduit to engage multiple surfaces of the conduit and in which at least two of these surfaces are separated by a distance less than 10 times the internal cross-sectional diameter of the conduit.
The lead-in section is preferably a substantially straight section of tubing which is at least 2 meters long. The tubing can be a straight section of the conduit.
The lead-in section is preferably of such a design that if the conduit is detached from the lead-in section, and transport of the cable through the lead-in section commenced using the cable installation means, then the cable will continue to be transported through the lead-in section if a tensile load of up to 1 Newton is applied to the cable at the exit of the lead-in section for more than one minute, and where the cable will start to transport again if the motion of the cable is stalled at the exit of the lead-in section for more than two seconds.
The sensor instrumentation need not be connected to the sensor while the sensor is transported through the conduit to the measurement location. In many instances it is preferable to remove the cable installation means and the lead-in section once the sensor is located at the measurement location, to form a seal around the cable where it enters or exits from the conduit, and then to connect the cable to the sensor instrumentation with a separate cable specially designed for surface cabling.
The invention also provides a method of installing a sensor at a measurement location comprising the steps of pumping the sensor and a cable through a conduit, forming a seal around the cable where it enters the conduit, and connecting the cable to the sensor instrumentation.
The sensor can be an optical fibre sensor which is connected to the cable. Alternatively, the sensor can be a micromachined sensor which is connected to a cable.
The cable can be one or more optical fibre cables. These can be hermetically sealed with carbon coating, can have high-temperature coatings such as polyimide, or silicone or polytetrafluoroethelene, metals such as nickel or indium or aluminium, or can have combinations of these coatings.
The conduit can be installed such that it extends to the measurement location prior to pumping the sensor and the cable through the conduit. In some instances, it can be preferable to pump the sensor and the cable through the conduit, and then to place the conduit such that the sensor is located at the measurement location.
An example is where the sensor and cable is pumped into the conduit and then the conduit is subsequently lowered into an oil well in order to take a measurement. The conduit can then be removed from the oil well and lowered into one or more oil wells to repeat the measurement. It will be appreciated that it can be preferable to weight the conduit prior to lowering it into the oil well. The conduit when inserted into the oil well can be configured as a single channel from the surface into the oil well, or can be configured such that it extends into the oil well and then returns back to the surface again.
The sensor can be an optical fibre sensor which is connected to the cable. Alternatively, the sensor can be a micromachined sensor which is connected to a cable.
The cable can be one or more optical fibre cable. These can be hermetically sealed with carbon coating, can have high-temperature coatings such as polyimide, or silicone or polytetrafluoroethelene, metals such as nickel or indium or aluminium, or can have combinations of these coatings.
In a first embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, in which the cable installation means includes a lead element attached to the sensor which ensures that the lead element is always able to contribute a net propelling force to avoid the sensor from stalling or to overcome a temporary stalling of the sensor while the fluid is flowing along the conduit. This is particularly advantageous when the sensor element is relatively stiff and cannot reliably circumvent bends in the conduit without touching the side walls of the conduit.
The fluid can be water or an organic liquid such as glycol or an oil. The fluid can be a silicone oil or polysiloxane oil. The fluid can be a non-Newtonian fluid such as a fluid containing solid suspensions, a gel, or a Bingham fluid. Examples of non-Newtonian fluids are drilling muds commonly used in the oil and gas industry. The fluid can be a combination of the above fluids.
In a second embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, which apparatus includes a first port where fluid enters into the conduit, and a first orifice through which the cable is able to be progressively pulled while deploying the sensor, and in which the orifice is such that sufficient fluid flows through the conduit in order to transport the sensor to the measurement location.
The first orifice can comprise a deformable insert which can be deformed in order to provide a close fit around the cable as it is being pulled through the deformable insert. Such an arrangement is commonly referred to as a stuffing box, and is common in the oil industry in slickline operations.
The first orifice can comprise a wireline injector suitably modified for small diameter cables such as optical fibre cables. Care must be taken with such an injector not to use grease which can coat the fibre and cause it to stick to the wall of the conduit.
The first orifice can include a capillary, preferably of a material such as stainless steel, connected to the lead-in section through which the cable is able to be progressively pulled while deploying the sensor. The capillary can preferably be designed to form a close fit around the cable to prevent excessive fluid escaping through the capillary. Its entry can preferably be shaped so as not to damage the cable.
The lead-in section can include a diameter restriction in order to reduce the pressure of the fluid at the end of the capillary where the cable enters into the lead-in section. The advantage is to reduce the backward force on the cable, to increase the forward drag on the cable at the capillary exit, and to reduce fluid loss through the capillary. The diameter restriction is preferably designed with an adiabatically reducing taper followed by an adiabatically increasing taper in order to minimise the overall pressure loss in the lead-in section as measured after and before the diameter restriction means.
In a third embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, which apparatus includes an exit port at the end of the lead-in section in order to increase the rate that fluid flows in the lead-in section and thus increase the fluid drag on the cable in the lead-in section.
The exit port can include a valve which is preferably closed once the sensor has reached it.
The exit port can be configured to ensure that the fluid flowing through the exit port does not create excessive turbulence in the conduit.
In a fourth embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, which apparatus includes a first port where the fluid enters into the lead-in section, a first orifice and a second orifice through which the cable is able to be progressively pulled while deploying the sensor, and a second port for reducing the fluid flowing through the second orifice, in which the first and second orifice are configured such that sufficient fluid flows through the conduit in order to transport the sensor to the measurement location.
The second port can be connected to the means for propelling the fluid along the conduit. Such an arrangement is useful in oil well applications for reducing the risk of gases such as light hydrocarbons or hydrogen sulphide or other poisonous gases escaping from the conduit through the second orifice means.
The apparatus can include a plurality of orifices, in which each orifice contains at least one port for progressively reducing the fluid flowing through each orifice from the conduit. The fluid flowing through each port can be regulated using valves or chokes.
According to a fifth embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, which apparatus includes a first port where the fluid enters into the conduit, a first orifice through which the cable can be progressively pulled while deploying the sensor, and in which the cable installation means includes pay-out controller for controlling the rate at which the cable deploys.
The pay-out controller is preferably configured to limit the rate at which the cable is deployed, and to make the rate at which the cable is deployed independent of the fluid flow rate. It is important for reliable deployment to ensure that the rate at which the cable is deployed into the lead-in section is no greater than the rate at which the cable is being transported in subsequent sections of the conduit. Failure to observe this condition can lead to the cable xe2x80x9cpiling upxe2x80x9d within the conduitxe2x80x94a condition which is difficult to cure.
In the event that the cable has been caused to pile up at a point in the conduit remote from the lead in section, it can be useful to restrain the rate at which the cable can be fed into the conduit, while increasing the fluid drag on the cable in the conduit and thereby clearing the pile up.
The pay-out controller can include a wheel assembly for progressively pulling the cable through the first orifice means.
The pay-out controller can alternatively be located on the other side of the first orifice and can limit the rate at which the cable is pulled through the first orifice.
According to a sixth embodiment of the invention, there is provided apparatus for the remote measurement of physical parameters, in which the cable installation means includes a first port where the fluid enters into the conduit, and a sealed container for holding the sensor and the cable prior to pumping the sensor to the measurement location.
The invention further includes a method and apparatus for removing an optical fiber and an optical fiber sensor from oil well, regardless of the method by which the fiber and the sensor have been deployed into the well. In the method, fluid is propelled through the conduit containing the optical fiber and the sensor using the method and apparatus described above for installing an optical fiber into a conduit to drive the fiber and the sensor out of the conduit. When the conduit is a one-way conduit having one end terminating in an opening dispose within the well, the fiber and the sensor are pumped from the conduit into the well. When the conduit is a two-way conduit having both ends terminating in openings outside of the well, the fiber and the sensor are pumped from the conduit and can be collected outside of the well.